Contamination over power line insulator-strings is a major source of power quality impairment. Such contamination can cause flashovers, which result in shortcuts and wide-area power sags (instantaneous voltage level drop). This causes significant damage to industrial power consumers. Electrical companies invest significant resources on washing insulator strings using helicopters and from the ground. Currently, the maintenance crews cannot get a view of the contamination level in power transmission and distribution lines, and selecting the sections that needs to be washed is based mainly on the experience of the maintenance teams.
Different systems and methods have been proposed in the past for detecting contamination over power line insulators. Most of the methods are using a dedicated sensor per each insulator string—for example see Yuan Jing, Chinese patent CN1306213A. These methods are not cost efficient as there are many strings per each tower, and many devices need to be purchased and deployed.
Other methods include using pilot isolators, which are used to sample contamination, for example see Baba Motoharu, JP patent number JP2008123805A. Since pilot insulators are used for prediction of contamination instead of using data from the actual insulator strings of the power-transmission system, these methods can offer only a limited level of prediction of flashovers on the actual transmission system.
It is well known, that partial discharges are developed over contaminated or damaged insulator string before a flashover occurs, and some prior art methods detect pulses which result from partial discharges over the insulator string in order to predict flashovers over the insulator strings. However, these methods do not prove efficient algorithms for localizing a contaminated insulator, generating partial discharges pulses, and therefore many sensors need to be deployed in order to estimate the location of the contaminated insulator, typically at least one sensor per tower. This increases the cost of the solution. Some prior art methods apply a threshold in order to count PD (partial discharge on the surface of insulators) pulses. This scheme requires setting the threshold in advance, and precludes post-measurement analysis.